The invention pertains to a warp knitted fabric having large grid openings, especially a Geo-grid, and a method for the production of such a warp knitted fabric which exhibits a biaxial, specifically a textile structure, having stay- and weft threads being arranged in groups in a crossing array.
Such knitted structures having large grid-like openings are applicable, especially as Geo-grid fabrics, in different regional as well as civil areas. For example, in the highway construction as a reinforcement for asphalt, as a reinforcement in the banks of canals or as a reinforcement for an embankment in man-made slopes.
Warp knitted fabrics with large grid openings, simply called Geo-grid fabrics hereafter, are also used as an intermediate product in the production of, for example, reinforced planar foiles, in plaster and cement reinforcements or as a carrier in layered products, all because of its specific characteristics that is, low weight, low cost and good permeability.
Heretofore Geo-grids, produced under currently known methods, consist of stay- and weft threads being combined crosswise in groups relative to each other which are firmly connected to or knitted with each other by so-called warp threads which form stitches. The continuously formed stitches around the stay threads serve as an additional stabilizing factor at the crossing points of the stay- and the weft threads as well as in the spacing between the crossing points of the Geo-grid material. However it has been shown, as a disadvantage. that the speed of the production of such a Geo-grid fabric cannot be raised, during a short term duration of the RPM of the machine and the concomitant high frequency of stitch forming because it is technically not feasible .
DE 198 16 440 C1 describes a method for the production of a warp knitted fabric in which arbitrary pattern variations with differing pattern repeats can be produced by lateral conveyors which vary in their speeds. In this arrangement, the lateral conveyor is driven independently from the drive of the knitting machine. This method is unsuitable in the efficient production of a Geo-grid fabric having an unchanged grid pattern because the production speed finally cannot be increased. One can merely obtain variable grid spacings by way of the differing speeds of the lateral conveyors but not, however, by variable pull-off speeds of the knitted fabric.